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| Titel |
Impacts of changes in vegetation cover on soil water heat coupling in an alpine meadow of the Qinghai-Tibet Plateau, China |
| VerfasserIn |
W. Genxu, H. Hongchang, L. Guangsheng, L. Na |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 13, no. 3 ; Nr. 13, no. 3 (2009-03-13), S.327-341 |
| Datensatznummer |
250011798
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| Publikation (Nr.) |
 copernicus.org/hess-13-327-2009.pdf |
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| Zusammenfassung |
| Alpine meadow is one of the most widespread grassland
types in the permafrost regions of the Qinghai-Tibet Plateau, and the
transmission of coupled soil water heat is one of the most crucial processes
influencing cyclic variations in the hydrology of frozen soil regions,
especially under different vegetation covers. The present study assesses the
impact of changes in vegetation cover on the coupling of soil water and heat
in a permafrost region. Soil moisture (θv), soil temperature
(Ts), soil heat content, and differences in θv−Ts coupling were
monitored on a seasonal and daily basis under three different vegetation
covers (30, 65, and 93%) on both thawed and frozen soils. Regression
analysis of θv vs. Ts plots under different levels of vegetation cover
indicates that soil freeze-thaw processes were significantly affected by
the changes in vegetation cover. The decrease in vegetation cover of an
alpine meadow reduced the difference between air temperature and ground
temperature (ΔTa−s), and it also resulted in a decrease in
Ts at which soil froze, and an increase in the temperature at which it
thawed. This was reflected in a greater response of soil temperature to
changes in air temperature (Ta). For ΔTa−s outside the range
of −0.1 to 1.0°C, root zone soil-water temperatures showed a
significant increase with increasing ΔTa−s; however, the
magnitude of this relationship was dampened with increasing vegetation
cover. At the time of maximum water content in the thawing season, the soil
temperature decreased with increasing vegetation. Changes in vegetation
cover also led to variations in θv−Ts coupling. With the increase
in vegetation cover, the surface heat flux decreased. Soil heat storage at
20 cm in depth increased with increasing vegetation cover, and the heat flux
that was downwardly transmitted decreased. The soil property varied greatly
under different vegetation covers, causing the variation of heat
conductivity and water-heat hold capacity in topsoil layer in different
vegetation cover. The variation of heat budget and transmitting in soil is
the main factor that causes changes in soil thawing and freezing processes,
and θv−Ts coupling relationship under different vegetation
fractions. In addition to providing insulation against soil warming,
vegetation in alpine meadows within the permafrost region also would slow
down the response of permafrost to climatic warming via the
greater water-holding capacity of its root zone. Such vegetation may
therefore play an important role in conserving water in alpine meadows and
maintaining the stability of engineering works constructed within frozen
soil of the Qinghai-Tibet Plateau. |
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